A test for comparing the means of two samples, or the mean of one sample (or even parameter estimates) with a specified value; also known as the "Student t-test" after the pseudonym of its inventor.

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30 views

Am I causing statistical violations?

I am trying to analyze where the significant differences are between 2 sets of time series. Group 1 (Expert) has 29 trials normalised to 256 points whereas Group 2 (Novice) has 19 trials (see attached ...
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10 views

Interpreting test results on log-transformed data

I have data that is not normally distributed. I can log-transform it to be normally distributed, and then perform, for example, a t-test. But how do I interpret the results of the t-test? Do I have ...
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0answers
12 views

Using a t-test for paired proportions

This is something that I'm having trouble verifying on Google, so I'm asking here as a sanity check. I have data collected randomly (not equally) over time for different users. To determine if some ...
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0answers
22 views

t-test in large, unequal sample size + additional info such as effect size

I have 2 samples, named "1" and "3": (1) n = 1282, mean = 14.77, sd = 8.27 (3) n = 5360, mean = 15.88, sd = 8.55 Their distribution look: ...
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0answers
14 views

What scale to use for likert data [on hold]

I am currently in the middle of writing my dissertation and I have reached the area where I am meant to be analysing the data. I used a likert scale for my questionnaire and now i have got the data ...
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7 views

Is this a paired or independent sample [on hold]

If I am comparing the speed of lions and cheetahs, would this be a paired sample or independent sample
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1answer
23 views

Equivalence of the dt and pt function in R

in my own curiosity I decided to question the equivalence of dt and pt in R. pt denotes the cumulative density function of the t-distribution. So this gives us $P(X \le x)$. So if I want to find the ...
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1answer
25 views

How to combine 2 unpaired t tests that test the same effect

I have am studying an effect that degrades device quality and performed an independent sample test on two batches that had different initial quality. I would like to make the strongest statement ...
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0answers
9 views

Calculate Sample Size for a Price Change for Specific Group

Say I operate a tour bus. For every tour I run, I offer guests the option to buy a camera. The camera currently costs 5. I know average purchase rate is 40 percent and the standard deviation per ...
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14 views

Comparing multiple effects of treatment

I am measuring gait in PD patients undergoing surgery. I measure them pre-operation and then at 6 months post-operation. I want to answer the question how does their gait improve. I am reporting 13 ...
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0answers
2 views

How to test whether correlate personality ratings with behavioural observations

I'm running a study to test whether personality (Big Five) predicts problem solving in children (N=200), and was wondering whether anyone could help with the best approach for analysis. I've collected ...
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15 views

Given two normally distributed random variables, how can I find the largest standard deviation so that $p<\alpha$ using Student's t-test? [closed]

Suppose $X\sim N(\mu_{X}, \sigma^{2})$ and $Y\sim N(\mu_{Y}, \sigma^{2})$. If $\mu_{X}$ and $\mu_{Y}$ are known, how can I find the largest pooled standard deviation for the Student's t-test so that ...
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7 views

Interpreting Tukey test for significant differences

Hi I have 38 categories and I have their means. I want to see if the differences in means are significantly different. I ran an anova and the p-value is <2e-16. Then I wanted to investigate ...
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0answers
5 views

Spearman correlation and ranksum test for 2-class problems

While Pearson correlation and 2-sample T test give the same p value and the correlation coefficient can be easily converted into t-value in 2-class problems, Spearman correlation and Wilcoxon ranksum ...
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1answer
25 views

Testing the difference between two samples with very different sizes using an un-paired t-test

I want to test wether population A is significantly different from population B (at 5% confidence interval). I need to do it for each variable using an un-paired t-test, since my data are normally ...
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1answer
35 views

Why is the degree of freedom in t.test dependent on setting of digits?

This seems to be a very basic problem but I just can't seem to figure out why it happens. Why is the degree of freedom in t.test in ...
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0answers
8 views

Statistical significance in a small peer group

I am looking at the gross profit margins in a industry where there are 10 companies. The company I am interested in has a gross profit margin of 28% and the mean gross margin across all 10 companies ...
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0answers
5 views

Mean accuracy confidence intervals with “corrected resampled t-test statistic”

I'm interested in calculating the expected prediction accuracy of my machine learning algorithm. My datasets only contain a small number of sample, so to do this, I repeat k-fold cross validation ...
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1answer
20 views

T-test for percentage change

Suppose I have some paired data (for example weight before and after), and I wish to find a confidence interval for the percentage increase in weight, can I simply apply the t-test to the percentage ...
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2answers
23 views

Interpreting contradicting results T-Test vs. Mann-Whitney test (2 independent samples)

I want to test if two indepent experimental groups are sign. different in terms of one outcome variable, but face the following questions: Basic setup 2 groups with 200 observations each Outcome ...
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24 views

Sampling distribution of t values

In my experiment, analysis is performed on the single subject level such that for each subject I get a t value*. the degrees of freedom are identical for all subjects. I would now like to ask whether ...
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1answer
36 views

Bootstrapping a t-test in R

I have two groups of individuals (22 in each group), which I compared using a t-test. The difference between groups was non-significant (p = .17). Because the p-value was quite low, my supervisor ...
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0answers
13 views

Interpreting results of Libreoffice Calc's TTEST function [duplicate]

I'm doing some data analysis on a small dataset (35 individuals) and I'm wondering whether my findings are statistically significant. Individuals are asked questions before and after a treatment, so ...
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1answer
30 views

Bootstrapping and comparing mean distributions

Is the following a reasonable approach to assess the statistical significance of the difference between two groups' For each group 1) Subsample with replacement 2) Take the mean of the subsample 3) ...
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1answer
18 views

Two-way ANOVA doesn't detect differences between conditions in a specific group?

OK, so let's say we have independent variables Condition (A or B) and Race (1 or 2 or 3). Then say we have a dependent variable X. We can run a two-way ANOVA to find out if there's an effect due to ...
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2answers
25 views

Bootstrapping a t statistic - Rationale and procedure

I was hoping someone could help me out with this. I've seen similar questions on the forum, but I need to know if I've understood the correct rationale and procedure for bootstrapping for my ...
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1answer
32 views

Why do we ignore the main effects when the interactions are not significant in a three-way ANOVA?

I'm following an SPSS guide online, and the procedure is to first test for a three-way interaction. In my case there was no sig. three-way interaction. Then the procedure asks me to consider two-way ...
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1answer
27 views

Testing Clustering Variables

I have two clusters. Those two clusters were obtained using Fuzzy C-Means with 8 variables. I'd like to know which variables have important role in differentiating the two clusters. Can I use t test ...
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1answer
40 views

Is it appropriate to use t-tests to find the most different outcomes?

I have a large CSV file of spending by individuals on different drugs. I want to find the drugs with the most different spending patterns by gender. The file looks a bit like this, but with 7.5k ...
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48 views

T tests on proportions - Wrong, but how wrong?

In psychology, and probably a number of other disciplines, it's common practice to test between-groups effects on a binary variable, such as accuracy, by aggregating data within participants, and then ...
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1answer
63 views

How to analyze data once broken down into gender, race, etc

I have two conditions, Treatment A, and Treatment B. Participants are randomly assigned to a treatment at the outset. Then I run unpaired t-tests on the data to find any differences. BUT I am also ...
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2answers
129 views

Logistic regression or T test?

A group of persons answers one question. The answer can be "yes" or "no". The researcher wants to know whether age is associated with the type of answer. The association was assessed by doing a ...
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0answers
22 views

Using regression fit to compare two groups at a time point

I have estimated a regression model in R with two groups, included as factors. Their regression fits are visually quite different, but I would like to statistically test if they are different on a ...
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21 views

what does value of t test mean? [duplicate]

I have two distribution of one variable and I've used t test to find how much they are significantly different. But I'm not very familiar with this test and don't know what does this values mean? is ...
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1answer
53 views

1 and 2 sample t-tests for plants and soils question!

I have a good friend who has an experiment where he grows different kind of plants on various soils and measures the protein content and weight each week for 5 weeks. His goal is to determine which ...
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0answers
20 views

How do I calculate a t-score from a p-value (gain scores and N also available)

I have this problem that only the gain scores with the p-value of a t-test are given in a scientific article. The authors neglected to report the t-test statistic and I'm stuck on figuring out how to ...
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2answers
34 views

Can a linear relationship between estimated standard deviations and estimated means be used to increase the power of a t-test?

Let’s say I have a high number of treatments (40) but a low number of replications per treatment (n=4), and I am interested in comparing values between two particular treatments (let’s say treatments ...
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0answers
13 views

Mixed ANOVA interaction effect - How do I which treatment was more effective?

I have conducted a mixed between-within ANOVA with 3 intervention groups and 2 measurement times (pre/post) in SPSS. There was a significant Time*Group interaction, but significant main effects. How ...
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0answers
19 views

What is equivalent of pairwise t-test for categorical variables?

I am doing some analysis where I have two monthly snapshot data (containing both numeric and categorical variable). Now I am trying to see which variable changed significantly from the first month in ...
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0answers
31 views

Choosing the correct experimental design

So lets just say I conducted a chi-squared contingency analysis test (I did btw) on 40 separate fish. Each individual fish only went through one treatment trial, where they were subjected to ...
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0answers
16 views

Multiple Comparisons for paired control and treatment groups

I want to conduct a post-hoc analysis on the impact of a treatment compared to the control Each control and treatment were selected to that the underline features are similar. For e.g. in the ...
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0answers
19 views

Significance of excess return using geometric mean

Since I am writting an assignement about a contrarian-strategy I have to test if the excess returns are significant or not. I calculated the excess returns this way: geomean(pf_returns) - ...
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3answers
49 views

Is ANOVA the same as running 3 t-tests?

I have a group of subjects which did tests under 3 different conditions. If I now want to compare variables with a ANOVA, is it right that I get the same p-values as if I would run 3 t-tests ...
2
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1answer
25 views

Does the bonferonni correction change the outcome of the p-value or is it just changin what you accept as significant?

For some reason I can't seem to integrate the bonferonni corrected p adjustment into my multiple comparisons t test in r so I need to do each of my 3 tests individually. What I wondered was do I need ...
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0answers
10 views

ttest in sas with proc ttest

I have a data with GENDER=(1/0) INCOME SENIORITY=(1/0). I need to run a ttest on INCOME by GENDER for SENIORITY=1. As far as I know, the default of HO=0, which means that there is no difference ...
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1answer
29 views

Testing for three means in order

Say I have data as follows: type|value where type takes values $A$, $B$ and $C$ and value is ...
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0answers
9 views

Paired data measured over different timeframe analysis

For number of patients I have two measurements of the same characteristic. For example: patient 1: one measured value at date1 and second measured value at date2 patient 2: one measured value at ...
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1answer
51 views

Testing for Significance - Should t-test be used or paired t-test

Let's say there are 100 stock exchanges on which I trade stocks and the cost of me trading has the averages below ...
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1answer
40 views

Similarity between two small datasets

I have gone through several test's (Kolmogorov-Smirnov, t-test, u-test etc..) but I am not sure which one to use when it comes to comparing two small data sets, lets say of size 10 each. ...
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6 views

Which test to do for comparison effect context over time

I'm currently working on my dissertation, and have finally gotten to the point to where I can conduct the analyses for my hypotheses. My main hypothesis is: 'Study organizations have a positive ...